After downgrading to an older version of Antigravity, asking the agent anything would only result in this response: “This version of Antigravity is no longer supported. Please upgrade to receive the latest features.”
However, I discovered a surprisingly simple fix. All you need to do is open \AppData\Local\Programs\Antigravity IDE\resources\app\product.json and change the value of ideVersion to the latest version number. It works perfectly!